1. Field of Invention
This invention relates generally to tests for determining the suitability of staple fiber for use in textile processing operations. More particularly, it relates to a card web strength test that has utility both as a research tool and as an early warning system for production purposes.
2. Prior Art
Carding machines for converting staple fiber into carded webs are extremely old in the art. Generally, the carded web is immediately converged and partially drafted to form a sliver. Thereafter it is conventionally converted into spun yarn.
Likewise, it has been known for a very long time that the strength of the carded web significantly affects both downstream processability and the properties of the products obtained. Obviously, when the strength of part of the web falls below the forces imposed upon that portion of the web, a hole appears therein. Further, borderline conditions resulting in low strength in part of the web can lead to variability in the subsequent product of properties such as neps, imperfections, weight per yard, tenacity, elongation, and evenness.
There is no existing ASTM test for measuring the strength of a carded web. At best, there have been only subjective and/or indirect tests such as those discussed briefly below.
The "Maximum Web Draft Ratio" test is obvious from its name. Such test cannot be used on a production plant to continuously monitor the production product.
The "Sliver Shake Test Rating" is a coarse subjective test that is relatively insensitive to threshold weakening of the web which generally takes place preferentially at the edges of the web. Observed results depend to some extent upon the weight of the web.
The "Blow" test is a test that has been used for many years, in which the operator blows on the edge of the web and observes whether there is a tendency for the web to fall apart. It is crudely subjective and the observed results depend upon the weight of the web.
"Sliver Cohesion" is another test that has been used, with the test results being expressed in grams/grain/yard. It is performed by measuring the force required to draft a sliver a specified amount between two sets of rolls. A Custom Scientific CS 83 Tester or similar device can be used. However, such test results have tended to show lack of close correlation with staple properties and textile processing performance, particularly at the carding process.